IVF Conception Tied To Greater Cancer Risk In Children With Birth Defects

Among children with birth defects, those conceived via in vitro fertilization (IVF) were at greater risk of developing cancer in a cohort study than those conceived naturally, although a birth defect increased the risk of cancer across the board.

"Pregnancies conceived with IVF are known to be at higher risk for adverse outcomes, including prematurity, gestational hypertension, and placental complications, and the children are at greater risk for birth defects," Dr. Barbara Luke of Michigan State University in East Lansing told Reuters Health by email.

The group's previous evaluation of the risk of childhood cancer among children in 14 US states was based on more than 275,000 IVF-conceived children and 2.26 million control children born in 2004-13. That study, published in 2019, found no increased cancer risk overall, but a small elevated risk of embryonal tumors. (http://bit.ly/2HRyovk).

The current study is the result of continued research in four of the original states (New York, North Carolina, Massachusetts, and Texas). As reported in JAMA Network Open, the study included more than one million children conceived naturally (51.3% boys; 69.7% white) and more than 52,000 conceived via IVF (51.3%boys; 81.3% white) using autologous oocytes and fresh embryos.

Children were followed for an average of 5.7 years.

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Cancer risks were higher among children with a major birth defect in the non-IVF (hazard ratio, 3.15) and IVF groups (HR, 6.90) compared with children without birth defects.

The HR of cancer among children with a major nonchromosomal defect was 2.07 in the non-IVF group and 4.04 in the IVF group.

By contrast, the HR of cancer among children with a chromosomal defect was 15.45 in the non-IVF group and 38.91 in the IVF group.

Dr. Luke noted, "An unresolved question in assisted reproduction research remains the contribution of parental versus treatment factors to adverse outcomes. Most likely it is a combination of both factors and warrants continued research in all areas."

"IVF-conceived children are at about one-third greater risk of birth defects compared to their naturally-conceived counterparts, as well as at higher risk of childhood cancer, although in absolute terms these numbers are small," she noted. "For example, among 100,000 naturally-conceived singleton children, an estimated 1,877 children would have a major birth defect and a total of 104 would develop childhood cancer (six of whom would have a birth defect)."

"By comparison," she said, "among 100,000 IVF-conceived singleton children (with autologous oocytes and fresh embryos), 2,457 would have a major birth defect and 161 would develop childhood cancer (24 of whom would have a major birth defect)."

Dr. Lisa Thiel, a perinatologist with Spectrum Health in Grand Rapids, Michigan, commented in an email to Reuters Health that women who require IVG "may have issues with egg or sperm quality, may be of advanced maternal age, and manipulation of embryos alone may slightly increase the risk of birth defects such as heart defects." She added, "The risk is low, however, important enough for our team to provide a cardiac echocardiogram at 22-26 weeks of gestation to evaluate further."

"IVF does not alone cause birth defects," she said. "Birth defects do not alone cause cancer. Birth defects and cancer are often multifactorial. They are associated."

"I do not feel that this study directly impacts the risk discussion for patient planning to undergo IVF at this time," she noted. "The discussion of overall risks including preeclampsia, preterm delivery, recommendations for fetal echo and quality prenatal care with appropriate monitoring are essential."

"The risk of cancer from IVF alone is not verified," she said. "We also do not have data to indicate which birth defects are linked to which types of cancers to counsel patients properly what to look for and monitor."

—Marilynn Larkin

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